This present invention relates generally to techniques for performing wellsite operations. More specifically, the present invention relates to techniques for preventing blowouts, for example, involving sealing a tubular at the wellsite.
Various oilfield operations may be performed to locate and gather valuable downhole fluids. Oil rigs are positioned at wellsites, and downhole tools, such as drilling tools, are deployed into the ground to reach subsurface reservoirs. Once the downhole tools form a wellbore (or borehole) to reach a desired reservoir, casings may be cemented into place within the wellbore, and the wellbore completed to initiate production of fluids from the reservoir. Tubulars (or tubular strings) may be positioned in the wellbore to enable the passage of subsurface fluids to the surface.
Leakage of subsurface fluids may pose an environmental threat if released from the wellbore. Equipment, such as blow out preventers (BOPs), may be positioned about the wellbore to form a seal about a tubular therein to prevent leakage of fluid as it is brought to the surface. Some BOPs may have selectively actuatable rams or ram bonnets, such as pipe or shear rams, that may be activated to seal and/or sever a tubular in a wellbore. Examples of BOPs and/or rams are provided in U.S. Pat. Nos. 7,367,396, 7,814,979, and 2011/0000670. Some BOPs may be spherical (or rotating or rotary) BOPs as described, for example, in U.S. Pat. Nos. 5,588,491 and 5,662,171, the entire contents of which are hereby incorporated by reference herein.